Haemophilus influenzae type b (Hib) is a major cause of bacterial meningitis in children under the age of five years. Protective antibodies to the disease are induced by the capsular polysaccharide of the organism and a vaccine was developed that utilises the purified polyribosyl ribitol phosphate (PRP) as the antigen. This vaccine provides 90% protection in adults and in children over 24 months of age, but was ineffective in children under 24 months Zangwill et al 1993 (The references are identified in a list of reference at the end of this disclosure). Like other polysaccharide antigens, PRP does not induce the proliferation of T-helper cells, and re-immunisation fails to elicit either a booster response or an increase in memory cells. Conjugation of the PRP polysaccharide with protein carriers confers T-cell dependent characteristics to the vaccine and substantially enhances the immunologic response to the PRP antigen. Currently, there are four PRP-carrier conjugate vaccines available. These are vaccines based upon H. influenzae type b capsular polysaccharide conjugated to diphtheria toxoid, tetanus toxoid, or Neisseria meningitidis outer membrane protein (reviewed in Zangwill et al 1993).
However, the current Haemophilus conjugate vaccines only protect against meningitis caused by Haemophilus influenzae type b. They do not protect against other invasive typeable strains (types a and c) and, more importantly, against non-typeable (NTHi) strains which are a common cause of postpartum and neonatal sepsis, pneumonia and otitis media. In the United States alone, treatment of otitis media costs between 1 and 2 billion dollars per year for antibiotics and surgical procedures, such as tonsillectomies, adenoidectomies and insertion of tympanostomy tubes. To achieve universal protection against H. influenzae related diseases in the 2 to 6 month age group and certain high risk groups, the provision of conserved, cross-reactive non-capsular H. influenzae immunogens is desirable. Methods for inducing immunity against disease are constantly improving and there is presently a move to use subunits and better defined materials as antigens. This is being undertaken to minimise or eliminate potential side-effects caused by certain native immunogens, while preserving their immunogenicity to confer protection against the disease. Therefore, it would be very attractive to develop a universal vaccine against Haemophilus using cross-reactive outer membrane proteins, fragment, analogs, and/or peptides corresponding thereto as protective antigens. Such antigens may be incorporated into the conventional H. influenzae type b conjugate vaccines as additional immunogens or used as autologous carriers for H. influenzae capsular polysaccharides. A high molecular weight outer membrane protein D15 found in non-typeable and type b stains of H. influenzae has been identified as a cross-reactive antigen (Thomas et al., 1990). D15 appears to be cell surface-exposed in its natural state and exhibits a molecular mass of about 80 kDa as judged by SDS-PAGE analysis. It would be desirable to provide the sequence of the DNA molecule that encodes this D15 outer membrane protein and peptides corresponding to portions thereof for diagnosis, immunization and the generation of diagnostic and immunological reagents. The diseases caused by Haemophilus are serious and improved methods for preventing, detecting and treating diseases such as otitis media, epiglottitis, pneumonia, and tracheobronchitis, are required.
The present invention is directed towards the provision of purified and isolated nucleic acid molecules comprising at least a portion coding for a D15 outer membrane protein of a species of Haemophilus. The nucleic acid molecules comprising at least a portion coding for D15 outer membrane protein are useful for the specific detection of strains of Haemophilus, and for diagnosis of infection by Haemophilus. The purified and isolated nucleic acid molecules, such as DNA comprising at least a portion coding for D15 outer membrane protein, are also useful for expression of the D15 gene by recombinant DNA means for providing, in an economical manner, purified and isolated D15 outer membrane protein.
The D15 outer membrane protein or fragments thereof or analogs thereof are useful immunogenic compositions for the preparation of vaccines against diseases caused by Haemophilus, the diagnosis of infection by Haemophilus and as tools for the generation of immunological reagents. mono- or polyclonal antisera (antibodies) raised against the D15 outer membrane protein produced in accordance with aspects of the present invention are useful for the diagnosis of infection by Haemophilus, specific detection of Haemophilus (in, for example, an vitro and in vivo assays) and for the treatment of diseases caused by infection by Haemophilus.
Peptides corresponding to portions of the D15 outer membrane protein or analogs thereof are useful immunogenic compositions for the preparation of vaccines against disease caused by Haemonhilus, the diagnosis of infection by Haemophilus and as tools for the generation of immunological reagents. Mono- or polyclonal antisera raised against these peptides, produced in accordance with aspects of the present invention, are useful for the diagnosis of infection by Haemophilus, specific detection of Haemophilus (in, for example, in vitro and in vivo assays) and for use in passive immunization as a treatment of disease caused by infection by Haemophilus. In accordance with one aspect of the present invention, therefore, there is provided a purified and isolated nucleic acid molecule, the molecule comprising at least a portion coding for a D15 outer membrane protein. The nucleic acid molecule has a DNA sequence selected from:
(a) the DNA sequence set out in any one of FIGS. 1A to 1E (as described below) or its complementary strand; and PA1 (b) DNA sequences which hybridize under stringent conditions to the DNA sequences defined in (a). The DNA sequences defined in (b) preferably has at least 90% sequence identity with the sequences defined in (a). The DNA sequence defined in (b) particularly may comprise the consensus sequence set forth in FIG. 1F (as described below).
In another aspect of the present invention, there is provided a purified and isolated D15 outer membrane protein or a portion thereof. The D15 outer membrane protein may be a Haemophilus D15 outer membrane protein and more particularly an H. influenzae D15 outer membrane protein and the H. influenza strain may be an H. influenzae type b strain, such as H. influenzae type b strains Ca or Eagan or MinnA or a non-typeable H. influenzae strain, such as PAK 12085 or SB33.
In an additional embodiment, the present invention also includes a recombinant plasmid adapted for transformation of a host, the recombinant plasmid comprising a plasmid vector into which has been inserted a DNA segment comprising the purified and isolated DNA molecule provided herein. Such recombinant plasmid comprises a plasmid vector into which a DNA segment which comprises at least an 18 bp fragment selected from the DNA molecules as recited above is inserted. The recombinant plasmid may be plasmid DS-712-2-1 having ATCC accession number 75604, deposited Nov. 4, 1993 and plasmid JB-1042-5-1 having ATCC accession number 75006, deposited Nov. 4, 1993.
The plasmids may be adapted for expression of the encoded D15 outer membrane protein in a host cell, which may be a heterologous or homologous host, by incorporation into a recombinant vector, provided in accordance with a further aspect of the invention. The recombinant vector may comprise at least a DNA segment comprising at least an 18 bp fragment selected from the DNA molecules as recited above and expression means operatively coupled to the DNA segment for expression of the gene product encoded thereby in the host cell. The plasmid for expression of the encoded D15 outer membrane protein may be plasmid DS-880-1-2 having ATCC accession number 75605, deposited Nov. 4, 1993 being adapted for expression at the D15 outer membrane protein in E. coli. The selected DNA segment may encode a polypeptide of at least 6 residues and, in particular, may be selected from those segments encoding a polypeptide of Table 2 (below). The DNA segment may further comprise a nucleic acid sequence encoding a leader sequence for export of the gene product from the host. The host for expression may be selected from, for example, Escherichia coli, Bacillus, Haemophilus, fungi, yeast or the baculovirus expression system may be used.
Additional aspects of the invention include the protein encoded by the DNA molecule comprising at least a portion coding for the D15 outer membrane protein, fragment or a functional analog of such protein, the use of the protein or analog in vaccination and diagnosis, and the generation of immunological reagents. The invention also includes antisera (antibodies) raised against the D15 outer membrane protein encoded by the DNA molecule comprising at least a portion coding for a D15 outer membrane protein and purified peptides corresponding to portions of the D15 outer membrane protein and there are in passive immunization and treatment of diseases caused by Haemophilus.
According to another aspect of the invention, a purified and isolated peptide containing an amino acid sequence corresponding to the amino acid sequence of at least a portion of the D15 outer membrane protein or variant or mutant which retains immunogenicity. The peptide may be produced by recombinant methods or peptide synthesis whereby the purified peptide is free from contaminants associated with bacteria normally containing the D15 outer membrane protein. Such synthetic peptides preferably have an amino acid sequence selected from those presented in Table 2.
In accordance with an additional aspect of the invention, an immunogenic composition is provided which comprises the D15 outer membrane protein, fragments thereof, functional analogs thereof, or peptides as recited above and a physiologically-acceptable carrier therefor. Such immunogenic composition is particularly formulated as a vaccine for in vivo administration to protect against diseases caused by Haemophilus. For such purpose, the immunogenic composition may be formulated as a microparticle preparation, capsule preparation or liposome preparation. In addition, such immunogenic composition may be provided in combination with a targeting molecule for delivery to specific cells of the immune system or to mucosal surfaces.
In accordance with a further aspect of the invention, there is provided a method for inducing protection against disease caused by Haemophilus, comprising the step of administering to a subject, including a mammal, such as a human, an effective amount of the immunogenic composition or the nucleic acid molecule as recited above to provide protective immunity against Haemophilus infection.
The present invention further includes a chimeric molecule comprising a D15 protein or peptide corresponding thereto as provided herein linked to another polypeptide or protein or a polysaccharide. The linked polypeptide or protein may comprise a surface protein or peptide corresponding thereto from a pathogenic bacteria, which may be the P1, P2 or P6 outer membrane protein of H. influenzae. The linked polysaccharide preferably comprise a PRP molecule from H. influenzae.